Make sure ListOf<T> converts sub-objects to T

Author: kevinushey

inst/include/Rcpp/vector/ListOf.h

@@ -31,10 +31,14 @@ class ListOf {
 
     ListOf(): list(R_NilValue) {}
 
-    ListOf(SEXP data_): list(data_) {}
+    ListOf(SEXP data_): list(data_) {
+        std::transform(list.begin(), list.end(), list.begin(), as<T>);
+    }
 
     template <typename U>
-    ListOf(const U& data_): list(data_) {}
+    ListOf(const U& data_): list(data_) {
+        std::transform(list.begin(), list.end(), list.begin(), as<T>);
+    }
 
     ListOf(const ListOf& other): list(other.list) {}
 

inst/unitTests/cpp/ListOf.cpp

@@ -93,3 +93,8 @@ int test_sub_calls(NVList x) {
 NumericVector test_nested_listof(ListOf< ListOf<NumericVector> > x) {
   return x[0][0];
 }
+
+// [[Rcpp::export]]
+ListOf<IntegerVector> test_return_IVList(List x) {
+    return x;
+}

inst/unitTests/runit.ListOf.R

@@ -74,4 +74,17 @@ if (.runThisTest) {
         )
     }
 
+    test.ListOf.convert.implicit <- function() {
+        checkEquals(
+            test_return_IVList(list(1, 2, 3)),
+            list(1L, 2L, 3L)
+        )
+    }
+
+    test.ListOf.convert.fail <- function() {
+        checkException(
+            test_return_IVList(list("a", "b", "c"))
+        )
+    }
+
 }